Following documentation for SSD upgrade for KB-000045830 results in error.

https://support.sophos.com/support/s/article/KB-000045830

Has the section:

Follow these steps to complete the installation:

Sign in to the CLI console and enter 4 for Device console.
To verify if the upgrade is available, enter the following command:
system ssd show
You will see the details if an upgrade is available.

Following those instructions I get:

Sophos Firmware Version: SFOS 20.0.0 GA-Build222
Model: XGS3300
Hostname: xxx-fw.xxx.com.au

console> system ssd show
% Error: Unknown Parameter 'ssd'